Characterisation and environmental application of an Australian natural zeolite for basic dye removal from aqueous solution

An Australian natural zeolite was collected, characterised and employed for basic dye adsorption in aqueous solution. The natural zeolite is mainly composed of clinoptiloite, quartz and mordenite and has cation-exchange capacity of 120 meq/100 g. The natural zeolite presents higher adsorption capacity for methylene blue than rhodamine B with the maximal adsorption capacity of 2.8 x 10(-5) and 7.9 x 10(-5) Mot/g at 50 degrees C for rhodamine B and methylene blue, respectively. Kinetic studies indicated that the adsorption followed the pseudo second-order kinetics and could be described as two-stage diffusion process. The adsorption isotherm could be fitted by the Langmuir and Freundlich models. Thermodynamic calculations showed that the adsorption is endothermic process with Delta H degrees at 2.0 and 8.7 kJ/mol for rhodamine B and methylene blue. It has also found that the regenerated zeolites by high-temperature calcination and Fenton oxidation showed similar adsorption capacity but lower than the fresh sample. Only 60% capacity could be recovered by the two regeneration techniques. (c) 2006 Elsevier B.V. All rights reserved.

Isomeric distribution and catalyzed isomerization of cobalt(III) complexes with pentadentate macrocyclic ligands. Importance of hydrogen bonding

We have investigated the isomeric distribution and rearrangement of complexes of the type [CoXLn](2+,3+) (where X = Cl-, OH-, H2O, and L-n represents a pentadentate 13-, 14-, and 15-membered tetraaza or diaza-dithia (N-4 or N2S2) macrocycle bearing a pendant primary amine). The preparative procedures for chloro complexes produced almost exclusively kinetically preferred cis isomers (where the pendant primary amine is cis to the chloro ligand) that can be separated by careful cation-exchange chromatography. For L-13 and L-14 the so-called cis-V isomer is isolated as the kinetic product, and for L-15 the cis-VI form (an N-based diastereomer) is the preferred, while for the L-14(S) complex both cis-V and trans-I forms are obtained. All these complexes rearrange to form stable trans isomers in which the pendent primary amine is trans to the monodentate aqua or hydroxo ligand, depending on pH and the workup procedure. In total 11 different complexes have been studied. From these, two different trans isomers of [CoCIL14S](2+) have been characterized crystallographically for the first time in addition to a new structure of cis-V-[CoCIL14S](2+); all were isolated as their chloride perchlorate salts. Two additional isomers have been identified and characterized by NMR as reaction intermediates. The remaining seven forms correspond to the complexes already known, produced in preparative procedures. The kinetic, thermal, and baric activation parameters for all the isomerization reactions have been determined and involve large activation enthalpies and positive volumes of activation. Activation entropies indicate a very important degree of hydrogen bonding in the reactivity of the complexes, confirmed by density functional theory studies on the stability of the different isomeric forms. The isomerization processes are not simple and even some unstable intermediates have been detected and characterized as part of the above-mentioned 11 forms of the complexes. A common reaction mechanism for the isomerization reactions has been proposed for all the complexes derived from the observed kinetic and solution behavior.

Using multivariate analysis to predict the behaviour of soils under effluent irrigation

Onsite wastewater treatment systems aim to assimilate domestic effluent into the environment. Unfortunately failure of such systems is common and inadequate effluent treatment can have serious environmental implications. The capacity of a particular soil to treat wastewater will change over time. The physical properties influence the rate of effluent movement through the soil and its chemical properties dictate the ability to renovate effluent. A research project was undertaken to determine the role that physical and chemical soil properties play in predicting the long-term behaviour of soil under effluent irrigation and to determine if they have a potential function as early indicators of adverse effects of effluent irrigation on treatment sustainability. Principal Component Analysis (PCA) and Cluster Analysis grouped the soils independently of their soil classifications and allowed us to distinguish the most suitable soils for sustainable long term effluent irrigation and determine the most influential soil parameters to characterise them. Multivariate analysis allowed a clear distinction between soils based on the cation exchange capacities. This in turn correlated well with the soil mineralogy. Mixed mineralogy soils in particular sodium or magnesium dominant soils are the most susceptible to dispersion under effluent irrigation. The soil Exchangeable Sodium Percentage (ESP) was identified as a crucial parameter and was highly correlated with percentage clay, electrical conductivity, exchangeable sodium, exchangeable magnesium and low Ca:Mg ratios (less than 0.5).

Adsorption study for removal of basic red dye using bentonite

Colored wastewater poses a challenge to the conventional wastewater treatment techniques. Solid-liquid phase adsorption has been found to be effective for the removal of dyes from effluent. In this paper, the ability of bentonite as an adsorbent for the removal of a commercial dye, Basic Red 2 (BR2), from an aqueous solution has been investigated under various experimental conditions. The adsorption kinetics was shown to be pseudo-second-order. It was found that bentonite had high adsorption capacity for BR2 due to cation exchange. The adsorption equilibrium data can be fitted well by the Langmuir adsorption isotherm model. The effect of the experimental parameters, such as temperature, salt, and pH was investigated through a number of batch adsorption experiments. It was found that the removal of dye increased with the increase in solution pH. However, the change of temperature (15-45 degrees C) and the addition of sodium chloride were found to have little effect on the adsorption process. The results show that electrostatic interactions are not dominant in the interaction between BR2 and bentonite. It was found that the adsorption was a rapid process with 80-90% of the dye removed within the first 2-3 min. Bentonite as an adsorbent is promising for color removal from wastewater.

Measurement of exchangeable cations in saline soils

The measurement of exchangeable cations in saline soils is limited by the difficulty in accurately separating soluble cations from exchangeable cations. A method is examined for saline soils in which exchangeable cations are calculated as the total extractable cations minus the concentration of soil solution (soluble) cations. In addition, a further two standard methods were investigated, one which assumes the total soil extractable cations are exchangeable, the other utilises a pretreatment to remove soluble salts prior to measurement of the remaining (exchangeable) cations. After equilibration with a range of sodium adsorption ratio (SAR) solutions at various ionic strengths, the exchangeable cation concentrations of two soils (Dermosol and Vertosol) were determined by these methods and compared to known values. The assumption that exchangeable cations can be estimated as the total soil extractable cations, although valid at low ionic strength, resulted in an overestimation of exchangeable Na and Ca concentrations at higher ionic strengths due to the presence of soluble salts. Pretreatment with ethanol and glycerol was found to effectively remove soluble salts thus allowing the accurate measurement of the effective cation exchange capacity (ECEC), however, dilution associated with the pretreatment process decreased concentrations of exchangeable Ca while simultaneously increasing exchangeable Na. Using the proposed method, good correlations were found between known and measured concentrations of exchangeable Na (Dermosol: y=0.873x and Vertosol: y=0.960x) and Ca (Dermosol: y=0.906x, and Vertosol: y=1.05x). Therefore, for soils with an ionic strength of approximately 50 mM (ECse 4 dS m-1) or greater (in which exchangeable cation concentrations are overestimated by assuming the total soil cations are exchangeable), concentrations can be calculated as difference between total extractable cations and soluble cations.

Continous annular chromatography for the separation of carbohydrate mixtures

The continuous separation of beet molasses resulting in a sucrose rich product and a non-sugar waste product was carried out using a rotating annular chromatograph. The annulus was 12 mm wide and 1.4 m long and was packed with a sodium charged 5.5% cross-linked polystyrene ion exchange resin. Separation was achieved by the simultaneous mechanisms of ion exclusion, size exclusion and partition chromatography. The entire packed bed was slowly rotated while beet molasses was fed continuously through a stationary feed nozzle to the top of the bed. Each molasses constituent having a different relative affinity for the packing and the deionised water mobile phase describes a characteristic helical path as it progresses from the stationary feed point to the bottom of the rotating bed. Each solute then elutes from the annulus at a different angular distance from the feed and separation of the multicomponent mixture is thereby achieved. When a 35% w/w sucrose beet molasses feed was used the throughput achievable was 45.1 kg sucrose m~3 resin h"1. In addition to beet molasses separation other carbohydrate mixtures were separated. In particular the separation of glucose and fructose by Ligand exchange chromatography on a calcium charged ion exchange bed was carried out. The effects of flowrates, concentration, rotation rate, temperature and particle size on resolution and dilution of constituents in the mixtures to be separated were studied. A small test rig was designed and built to determine the cause of liquid maldistribution around the annulus. The problem was caused by the porous bed support media becoming clogged with fines being introduced by eluent flows and off the resin. An outer ring was constructed to house the bed support which could be quickly replaced with the onset of maldistribution. The computer simulation of the operation of the rotating annular chromatograph has been carried out successfully.

Simultaneous biochemical reaction and separation in a continuous rotating annular chromatograph

The aim of this work has been to investigate the behaviour of a continuous rotating annular chromatograph (CRAC) under a combined biochemical reaction and separation duty. Two biochemical reactions have been employed, namely the inversion of sucrose to glucose and fructose in the presence of the enzyme invertase and the saccharification of liquefied starch to maltose and dextrin using the enzyme maltogenase. Simultaneous biochemical reaction and separation has been successfully carried out for the first time in a CRAC by inverting sucrose to fructose and glucose using the enzyme invertase and collecting continuously pure fractions of glucose and fructose from the base of the column. The CRAC was made of two concentric cylinders which form an annulus 140 cm long by 1.2 cm wide, giving an annular space of 14.5 dm3. The ion exchange resin used was an industrial grade calcium form Dowex 50W-X4 with a mean diameter of 150 microns. The mobile phase used was deionised and dearated water and contained the appropriate enzyme. The annular column was slowly rotated at speeds of up to 240°h-1 while the sucrose substrate was fed continuously through a stationary feed pipe to the top of the resin bed. A systematic investigation of the factors affecting the performance of the CRAC under simultaneous biochemical reaction and separation conditions was carried out by employing a factorial experimental procedure. The main factors affecting the performance of the system were found to be the feed rate, feed concentrations and eluent rate. Results from the experiments indicated that complete conversion could be achieved for feed concentrations of up to 50% w/v sucrose and at feed throughputs of up to 17.2 kg sucrose per m3 resin/h. The second enzymic reaction, namely the saccharification of liquefied starch to maltose employing the enzyme maltogenase has also been successfully carried out on a CRAC. Results from the experiments using soluble potato starch showed that conversions of up to 79% were obtained for a feed concentration of 15.5% w/v at a feed flowrate of 400 cm3/h. The product maltose obtained was over 95% pure. Mathematical modelling and computer simulation of the sucrose inversion system has been carried out. A finite difference method was used to solve the partial differential equations and the simulation results showed good agreement with the experimental results obtained.

Chemical modification of smectite clays

Today, speciality use organoclays are being developed for an increasingly large number of specific applications. Many of these, including use in cosmetics, polishes, greases and paints, require that the material be free from abrasive impurities so that the product retains a smooth `feel'. The traditional `wet' method preparation of organoclays inherently removes abrasives naturally present in the parent mineral clay, but it is time-consuming and expensive. The primary objective of this thesis was to explore the alternative `dry' method (which is both quicker and cheaper but which provides no refining of the parent clay) as a process, and to examine the nature of the organoclays produced, for the production of a wide range of commercially usable organophilic clays in a facile way. Natural Wyoming bentonite contains two quite different types of silicate surface (that of the clay mineral montmorillonite and that of a quartz impurity) that may interact with the cationic surfactant added in the `dry' process production of organoclays. However, it is oil shale, and not the quartz, that is chiefly responsible for the abrasive nature of the material, although air refinement in combination with the controlled milling of the bentonite as a pretreatment may offer a route to its removal. Ion exchange of Wyoming bentonite with a long chain quaternary ammonium salt using the `dry' process affords a partially exchanged, 69-78%, organoclay, with a monolayer formation of ammonium ions in the interlayer. Excess ion pairs are sorbed on the silicate surfaces of both the clay mineral and the quartz impurity phases. Such surface sorption is enhanced by the presence of very finely divided, super paramagnetic, Fe2O3 or Fe(O)(OH) contaminating the surfaces of the major mineral components. The sorbed material is labile to washing, and induces a measurable shielding of the 29Si nuclei in both clay and quartz phases in the MAS NMR experiment, due to an anisotropic magnetic susceptibility effect. XRD data for humidified samples reveal the interlamellar regions to be strongly hydrophobic, with the by-product sodium chloride being expelled to the external surfaces. Many organic cations will exchange onto a clay. The tetracationic cyclophane, and multipurpose receptor, cyclobis(paraquat-p-phenylene) undergoes ion exchange onto Wyoming bentonite to form a pillared clay with a very regular gallery height. The major plane of the cyclophane is normal to the silicate surfaces, thus allowing the cavity to remain available for complexation. A series of group VI substituted o-dimethoxybenzenes were introduced, and shown to participate in host/guest interactions with the cyclophane. Evidence is given which suggests that the binding of the host structure to a clay substrate offers advantages, not only of transportability and usability but of stability, to the charge-transfer complex which may prove useful in a variety of commercial applications. The fundamental relationship between particle size, cation exchange capacity and chemical composition of clays was also examined. For Wyoming bentonite the extent of isomorphous substitution increases with decreasing particle size, causing the CEC to similarly increase, although the isomorphous substitution site: edge site ratio remains invarient throughout the particle size range studied.

The release of nicotine from chewing gum formulations

The first clinically proven nicotine replacement product to obtain regulatory approval was Nicorette® gum. It provides a convenient way of delivering nicotine directly to the buccal cavity, thus, circumventing 'first-pass' elimination following gastrointestinal absorption. Since launch, Nicorette® gum has been investigated in numerous studies (clinical) which are often difficult to compare due to large variations in study design and degree of sophistication. In order to standardise testing, in 2000 the European Pharmacopoeia introduced an apparatus to investigate the in vitro release of drug substances from medical chewing gum. With use of the chewing machine, the main aims of this project were to determine factors that could affect release from Nicorette® gum, to develop an in vitro in vivo correlation and to investigate formulation variables on release of nicotine from gums. A standard in vitro test method was developed. The gum was placed in the chewing chamber with 40 mL of artificial saliva at 37'C and chewed at 60 chews per minute. The chew rate, the type of dissolution medium used, pH, volume, temperature and the ionic strength of the dissolution medium were altered to investigate the effects on release in vitro. It was found that increasing the temperature of the dissolution media and the rate at which the gums were chewed resulted in a greater release of nicotine, whilst increasing the ionic strength of the dissolution medium to 80 mM resulted in a lower release. The addition of 0.1 % sodium Jauryl sulphate to the artificial saliva was found to double the release of nicotine compared to the use of artificial saliva and water alone. Although altering the dissolution volume and the starting pH did not affect the release. The increase in pH may be insufficient to provide optimal conditions for nicotine absorption (since the rate at which nicotine is transported through the buccal membrane was found to be higher at pH values greater than 8.6 where nicotine is predominately unionised). Using a time mapping function, it was also possible to establish a level A in vitro in vivo correlation. 4 mg Nicorette® gum was chewed at various chew rates in vitro and correlated to an in vivo chew-out study. All chew rates used in vitro could be successfully used for IVIVC purposes, however statistically, chew rates of 10 and 20 chews per minute performed better than all other chew rates. Finally a series of nicotine gums was made to investigate the effect of formulation variables on release of nicotine from the gum. Using a directly compressible gum base, in comparison to Nicorette® the gums crumbled when chewed in vitro, resulting in a faster release of nicotine. To investigate the effect of altering the gum base, the concentration of sodium salts, sugar syrup, the form of the active drug, the addition sequence and the incorporation of surfactant into the gum, the traditional manufacturing method was used to make a series of gum formulations. Results showed that the time of addition of the active drug, the incorporation of surfactants and using different gum base all increased the release of nicotine from the gum. In contrast, reducing the concentration of sodium carbonate resulted in a lower release. Using a stronger nicotine ion-exchange resin delayed the release of nicotine from the gum, whilst altering the concentration of sugar syrup had little effect on the release but altered the texture of the gum.

Efficient purification of chromatin architectural proteins:histones, HMGB proteins and FKBP3 (FKBP25) immunophilin

A two-step process of high ionic strength lysis of chicken erythrocyte cell nuclei followed by cation-exchange chromatography has separated at very high yield all the histone and HMGB (high-mobility group B) nuclear proteins, except the less-soluble histone tetramers. Surprisingly high yields of the nuclear immunophilin FKBP3 (FKBP25) and Hsp70 (heat-shock protein 70) co-fractionate with HMGB1 and HMGB3. Furthermore, these proteins can be separated by anion-exchange chromatography. The purified nuclear proteins retain their native, post-translational modification (PTM) marks, including those associated with chromatin-fibre remodelling. These marks are intimately associated with the control of the cell cycle. The methods herein are therefore of value for targeting these and other nuclear proteins for future proteomic studies in healthy and diseased cells. This journal is © 2012 The Royal Society of Chemistry.

Novel organo-modifier for thermally-stable polymer-layered silicate nanocomposites

A new novel approach for the stabilisation of polymer-clay nanocomposites has been investigated based on reacting chemically an antioxidant function, a hindered phenol moiety, with an organic modifier based on a quaternary ammonium salt. The chemically linked antioxidant-containing organic modifier (AO-OM) was then introduced into natural montmorillonite (MMt) through a cation-exchange reaction resulting in antioxidant-containing organo-modified clay (AO-OM-MMt). The new antioxidant-containing modified clay, along with other organo-modified clays having a similar organo-modifier but without the reacted antioxidant, were characterised by spectroscopic, thermogravimetric and x-ray diffraction techniques and tested for their thermo-oxidative stability. PA11-based clay nanocomposites samples containing the AO-OM-MMt and the other organo-modified clays, both without and with an added (i.e. not chemically reacted) hindered phenol antioxidant (similar to the one used in the AO-OM) were prepared by melt processing and examined for their processing and long-term thermal-oxidative stability at high temperatures. It was shown that although the new organo-modifier, AO-OM, was also susceptible to the Hoffman elimination reaction, the nanocomposites containing this newly modified clay (PA11/AO-OM-MMt) showed higher melt processing and long-term thermo-oxidative stability, along with excellent clay dispersion and exfoliation, compared to the other PA11-nanocomposites examined here (with and without the conventionally added antioxidant). It is suggested here that the excellent overall performance observed for the PA11/AO-OM-MMt nanocomposites is due to an in-situ partial release of low molecular weight antioxidant species having stabilising functionalities that are capable of acting locally at the interface between the inorganic clay platelets and the polymeric matrix which is a critical area for the onset of degradation processes.

Synergistic synthesis of quasi-monocrystal CdS nanoboxes with high-energy facets

Hollow nanostructures with a highly oriented lattice structure and active facets are promising for catalytic applications, while their preparation via traditional approaches contains multiple steps and is time and energy consuming. Here, we demonstrate a new one-step strategy involving two complementary reactions which promote each other; it is capable of producing unique hollow nanoparticles. Specifically, we apply synergic cooperation of cation exchange and chemical etching to attack PbS nanosized cubes (NCs) and produce CdS quasi-monocrystal nanoboxes (QMNBs) which possess the smallest dimensions reported so far, a metastable zinc-blende phase, a large specific surface area, and particularly high-energy {100} facets directly visualized by aberration-corrected scanning transmission electron microscopy. These properties in combination allow the nanoboxes to acquire exceptional photocatalytic activities. As an extension of the approach, we use the same strategy to prepare Co9S8 and Cu7.2S4 single-crystal hollow nanooctahedrons (SCHNOs) successfully. Hence, the synergic reaction synthesis strategy exhibits great potential in engineering unique nanostructures with superior properties.

Interactions of different arsenic species with thols: Chemical and biological implications

Arsenic has been classified as a group I carcinogen. It has been ranked number one in the CERCLA priority list of hazardous substances due to its frequency, toxicity and potential for human exposure. Paradoxically, arsenic has been employed as a successful chemotherapeutic agent for acute promyelocytic leukemia and has found some success in multiple myeloma. Since arsenic toxicity and efficacy is species dependent, a speciation method, based on the complementary use of reverse phase and cation exchange chromatography, was developed. Inductively coupled plasma mass spectrometer (ICP-MS), as an element specific detector, and electrospray ionization mass spectrometer (ESI-MS), as a molecule specific detector, were employed. Low detection limits in the µg. L−1 range on the ICP-MS and mg. L−1 range on the ESI-MS were obtained. The developed methods were validated against each other through the use of a Deming plot. With the developed speciation method, the effects of both pH on the stability of As species and reduced glutathione (GSH) concentration on the formation and stability of arsenic glutathione complexes were studied. To identify arsenicals in multiple myeloma (MM) cell lines post arsenic trioxide (ATO) and darinaparsin (DAR) incubation, an extraction method based on the use of ultrasonic probe was developed. Extraction tools and solvents were evaluated and the effect of GSH concentration on the quantitation of arsenic glutathione (As-GSH) complexes in MM cell extracts was studied. The developed method was employed for the identification of metabolites in DAR incubated cell lines where the effect of extraction pH, DAR incubation concentration and incubation time on the relative distribution of the As metabolites was assessed. A new arsenic species, dimethyarsinothioyl glutathione (DMMTA V-GS), a pentavalent thiolated arsenical, was identified in the cell extracts through the use of liquid chromatography tandem mass spectrometry. The formation of the new metabolite in the extracts was dependent on the decomposition of s-dimethylarsino glutathione (DMA(GS)). These results have major implications in both the medical and toxicological fields of As because they involve the metabolism of a chemotherapeutic agent and the role sulfur compounds play in this mechanism.

Assessment of the occurrence and potential risks of pharmaceuticals and their metabolites in fish and water using liquid chromatography mass spectrometry

A comprehensive method for the analysis of 11 target pharmaceuticals representing multiple therapeutic classes was developed for biological tissues (fish) and water. Water samples were extracted using solid phase extraction (SPE), while fish tissue homogenates were extracted using accelerated solvent extraction (ASE) followed by mixed-mode cation exchange SPE cleanup and analyzed by liquid chromatography tandem mass spectrometry (LC-MS/MS). Among the 11 target pharmaceuticals analyzed, trimethoprim, caffeine, sulfamethoxazole, diphenhydramine, diltiazem, carbamazepine, erythromycin and fluoxetine were consistently detected in reclaimed water. On the other hand, caffeine, diphenhydramine and carbamazepine were consistently detected in fish and surface water samples. In order to understand the uptake and depuration of pharmaceuticals as well as bioconcentration factors (BCFs) under the worst-case conditions, mosquito fish were exposed to reclaimed water under static-renewal for 7 days, followed by a 14-day depuration phase in clean water. Characterization of the exposure media revealed the presence of 26 pharmaceuticals while 5 pharmaceuticals including caffeine, diphenhydramine, diltiazem, carbamazepine, and ibuprofen were present in the organisms as early as 5 h from the start of the exposure. Liquid chromatography ultra-high resolution Orbitrap mass spectrometry was explored as a tool to identify and quantify phase II pharmaceutical metabolites in reclaimed water. The resulting data confirmed the presence of acetyl-sulfamethoxazole and sulfamethoxazole glucuronide in reclaimed water. To my knowledge, this is the first known report of sulfamethoxazole glucuronide surviving intact through wastewater treatment plants and occurring in environmental water samples. Finally, five bioaccumulative pharmaceuticals including caffeine, carbamazepine, diltiazem, diphenhydramine and ibuprofen detected in reclaimed water were investigated regarding the acute and chronic risks to aquatic organisms. The results indicated a low potential risk of carbamazepine even under the worst case exposure scenario. Given the dilution factors that affect environmental releases, the risk of exposure to carbamazepine will be even more reduced.

Obtenção de organovermiculitas utilizando tensoativos e microemulsões e suas aplicações na separação de isômeros do Xileno

Surfactants are versatile organic compounds that have, in a single molecule, double chemical affinity. The surfactant molecule is composed by a hy drophobic tail group, a hydrocarbon chain (linear, branched, or mixed), and by a hydrophilic head group, which contains polar groups that makes it able to be applied in the organophilization process of natural clays. Microemulsions are microheterogeneous b lends composed by: a surfactant, an oily phase (non - polar solvent), an aqueous phase, and, sometimes, a co - surfactant (short - chain alcohol). They are systems with thermodynamic stability, transparent, and have high solubility power. Vermiculite is a clay m ineral with an expandable crystalline structure that has high cation exchange capacity. In this work vermiculite was used to obtain organoclays. The ionic surfactants dodecyl ammonium chlori de (DDAC) and cetyltrimethylammonium bromide (C 16 TAB) were used in the organophilization process. They were used as surfactant aqueous solutions and, for DDAC, as a microemulsion system. The organoclays were used to promote the separation of binary mixtures of xylene isomers (ortho - and meta - xylene). Dif ferent analytical techniques were used to characterize microemulsion systems and also the nanoclays. It was produced a water - rich microemulsion system with 0.92 nm droplet average diameter. The vermiculite used in this work has a cationic exchange capacity of 172 meq/100g and magnesium as main cation (24.25%). The basal spacing of natural vermiculite and organo - vermiculites were obtained by X - ray Diffraction technique. The basal spacing was 1.48nm for natural vermiculite, 4.01nm for CTAB - vermiculite (CTAB 4 ) , and 3.03nm for DDAC - vermiculite (DDAC M1A), that proves the intercalation process. Separation tests were carried out in glass columns using three binary mixtures of xylene (ortho - xylene and meta - xylene). The results showed that the organovermiculite pre sented an enhanced chemical affinity by the mixture of hydrocarbons, when compared with the natural vermiculite, and also its preference by ortho - xylene. A factorial experimental design 2 2 with triplicate at the central point was used to optimize the xylen e separation process. The experimental design revealed that the initial concentration of isomers in the mixture and the mass of organovermiculite were the significant factors for an improved separation of isomers. In the experiments carried out using a bin ary mixture of ortho - xylene and meta - xylene (2:1), after its percolating through the organovermiculite bed (DDAC M1), it was observed the preference of the organoclay by the ortho - xylene isomer, which was retained in greater quantity than the meta - xylene o ne. At the end of the treatment, it was obtained a final concentration in meta - xylene of 47.52%.